Relaxation oscillation generator



June 20, 1939. SCHLEQNGER I 2,163,214

RELAXATION OSCILLATION GENERATOR Filed Aug. 10, 1954 Patented June 20,1939 UNITED STATES RELAXATION OSCILLATION GENERATOR Kurt Schlesinger,Berlin, Germany, assignor to Radioaktiengesellschaft D. S. Loewe,Berlin- Steglitz, Germany Application August 10,

1934, Serial No. 739,301

In Germany August 14, 1933 3 Claims.

The present invention relates to relaxation oscillation generators intelevision apparatus, including a gas-filled, grid-controlled,thermionic tube, for producing line and frame deflecting voltages.

In the working of such apparatus as heretofore used severalinconveniences occur which are got rid of in an arrangement according tothe present invention.

One object of the invention is to provide means to give the discharge adefinite duration, which allows the discharge accurately to be governed,and to accelerate at the same time the break-down of the deflectingvoltage after ignition.

Another object of the invention is to provide means for compensating adeviation of the straight line form of the deflecting voltage.

A further object of the invention is to avoid interferences which may becaused by reaction of the amplifier to the discharge tube or of one ofthe two generators to the other one.

A further object of the invention is to avoid grid currents in thedischarge tube when it is in the state of ignition.

According to still a further feature of the invention, the grid bias ofthe discharge tube is taken from the anode Voltage supply in such amanner as to compensate fluctuations in the said supply with regard tothe influence exerted on the ignition moment.

The invention will be. more fully understood by reference to thefollowing detailed description in connection with the appended drawing,which shows diagrammatically a generator for producing deflectingvoltages according to the present invention.

In the drawing, I is the gas-filled thermionic tube, 2 the storagecondenser, 3 the charging resistance and 5 the indirectly heated cathodeof the tube, which is positively biassed in relation to the grid bymeans of the adjustable resistance 4. Since resistance 4 is fed by theanode potential, the grid bias undergoes all fluctuations of thispotential so that a shifting of the ignition moment by thesefluctuations is safely avoided. The charging potential is fed in throughsteadying means 2I, 22.

The control potentials are supplied to the grid of the tube I by theterminal 6 via a condenser O 24. The anode I of the tube I is connectedvia the coupling condenser with the control grid 8 of the screen gridamplifier tube 9. Thecontrol grid bias is fed in at IT via steadyingmeans 32, and the grid resistance. The bias of the screen grid I0 istapped at the potentiometer II in such manner that the commencingexponential curvature of the circuit charging the condenser 2 andconsequently of the deflecting voltage is compensated by the oppositecurvature in the characteristic of the tube 9. Remaining distortions ofthe straight line form of the deflecting voltage may be compensated by ahigh-pass filter consisting of condenser 25 and ohmic resistance 28connected in parallel, and inserted in the lead coupling both tubes. Theworking point on the characteristic is, by suitably biassing the controlgrid, made to be situated in the lower bend. From the anode I8 of theamplifier tube the amplified relaxation oscillation voltage potential(i. e. the potential drop across the anode resistance) is coupled by thecondenser I3 to the potentiometer I 4 which permits fine adjustment ofthe image size. The tap of this potentiometer is connected to theterminal I5, which may be connected directly with the deflecting systemof the Braun tube.

In the case of a tube I having cathodes of high emission, the condenser2 discharges in such a short time (about 1 micro-sec.) that theionisation does not disappear after quenching sufficiently quickly, atleast not in the line deflection tube. In this case irregularities occurin the ignitions of the tube, so that a disquietude appears over theentire image in a horizontal direction.

It has been found that this disquietude disappears entirely if theemission of the tube I is suitably reduced. This method, however, is bycertain reasons unsuitable in practice.

A satisfactory remedy against the irregularities in the initiation ofdischarge has been found in the use of a resistance I9 inserted in thedischarge circuit of the tube I. The resistance I9 is 100 ohms, with acapacity 2 of 2.10 mf., so that the duration of the discharge is atleast equal to or greater than the period of transmission ofan imagepoint, the time constant of the discharge circuit being approximately 2micro-sec.

It is important to connect the amplifier 9 with the anode of the tube Iand not with the condenser 2 directly. This has the effect that, becausein the moment of ignition the potential on the tube I drops much quickerthan that on the condenser, the cathode ray returns instantaneouslywithout to produce a visible line on the screen.

According to a further feature of the invention a resistance 20 of theorder of several ten-thousands ohms is provided in the lead to the gridof tube I, which safely prevents the main discharge arc, anode-cathodefrom partially flashing over to the grid and thereby causing anuncontrollably and unsteady leak current to flow. This measure is not sonecessary to be taken in the line frequency as in the frame frequencyoscillator.

Further, according to the invention the anode circuits of bothamplifiers are, as a whole, carefully screened off against therespective amplifier control grid circuits, taken as a whole, asindicated by the dotted line 30.

Furthermore, according to the invention, the line frequency arrangementand the frame-frequency arrangement are prevented from exerting anyinfluence on the working of each other by carefully screening-0E themagainst each other and by providing separate steadying means 32, 35 forthe control grid bias of the two amplifiers.

The amplifier tube 9 of the line-frequency arrangement is, according tothe invention, silvered on the inside and the silver coating passed toearth to prevent capacitative retroaction from being exerted by theamplified oscillations on the grid circuit of the discharge tube I,which Would cause a shifting of the ignition point. A silver coating ofthis nature in the amplifier tube of the frame-frequency arrangement maybe dispensed with because of the lower frequencies.

The single elements, for the production of a 180-line pattern, may beselected as follows:

Resistances Line frequency Frame frequency 3 1.2.megohms. 4 3,000 ohms3,000 ohms. l'1 10" ohms 10 ohms. 12 100.000 ohms, 14 Not higher than100,000 Not higher than 100,000

ohms. ohms. 100 ohms 30,000 ohms.

.1 inegohm. .5 megohm. 1 megohm. .1 megohm.

1 megohms- 0.1 megohm. 60,000 ohms Condensers Line irequency- Framefrequency plifier being coupled by a secondcondenser to the commonterminal of the first circuit and anode of said tube.

2. In a device according to claim 1, in which said circuit means.includes a grounded point and a biasing resistance between said cathodeand said grounded point.

3. In a device according to claim 1 having filtering elements in saidsecond mentioned circuit.

KURT SCHLESINGER.

